Your ignorance on this matter is showing. Women have done this for a while.
Schuyler Bailar, First D1 Transgender Swimmer, Joins Harvard's Men's Team
June 28, 2015
Schuyler Bailar, an incoming College freshman, will become the first openly transgender swimmer in NCAA Division I history when he joins the Harvard men’s swimming team for the upcoming season.
The swimmer’s journey—from a Harvard women’s swimming recruit to an incoming member of the men’s team—is a historic one in the world of college athletics.
Incoming College freshman Schuyler Bailar, the first openly transgender swimmer in NCAA Division I history, will swim with the Harvard men's team this upcoming season.
Bailar came out as transgender during his gap year after he graduated from high school a year ago. He had emerged as a top women’s swimming prospect at Georgetown Day School after setting more than 10 team records between 2010 and 2011 with a
club in his home state of Virginia. During his senior year, he was part of a team with Olympic gold medalist Katie Ledecky that set a national age group
record in the 400 yard relay.
By that time, Bailar had been recruited by Harvard women’s swimming and diving coach Stephanie Morawski, part of a strong Class of 2018. But Bailar did not enroll at Harvard immediately and instead took a year off.
While Bailar has always identified as male, he had not come out as transgender until after graduation. During his gap year he contemplated medically transitioning—something he initially thought might mean quitting the sport he loved.
“Initially the decision was, ‘Do I swim, or do I quit and transition?’” Bailar said. “I really didn’t want to give up swimming, but I also didn’t know how much longer I could do the living as a girl thing.”
He came up with a solution: He would get “top” surgery and swim on the women’s team, he informed a supportive Morawski in November.
While the first of those choices went as planned—the double mastectomy Bailar underwent in March removed his mammary glands and breasts—his thought process changed shortly before the surgery, in late February, when he received a call from his new coach.
Morawski’s words floored him. The coach said she had spoken with counterpart Kevin Tyrell, the coach of the Harvard men’s team: If Bailar wanted, he had the option of swimming on the men’s team.
The swimmer’s journey—from a Harvard women’s swimming recruit to an incoming member of the men’s team—is a historic one in the world of college athletics.
www.thecrimson.com
In 2019, Bailar completed his college career posting the "third fastest" time for 100-yard breaststroke for the Harvard team in the 2018–2019 season, and winning his third Ivy-League Championship ring as part of the Crimson's highest ranked team since the 1960–1961 season, which placed 8th at the 2019 NCAA Championships. Although Bailar began his college swimming career with low expectations, his final 100-yard breaststroke time ranked him in the top 15% of all NCAA men's swims for the season and in the top 34% of all NCAA Division 1 swims for the season.
en.wikipedia.org
This was 6-10 years ago and before Lia Thompson. And there are more.